Vacuum cleaners have a motor which typically drives an impeller to create a flow of air. The suction head of the vacuum cleaner has an opening in its bottom wall through which air can enter, the air carrying dirt and debris into the suction head. It is arranged that the air transports the dirt and debris by way of air flow ducts within the suction head, the ducts typically having a cross-sectional area measuring around 7 to 10 cm2. The dirt and debris is transported through the ducts to a dirt-collection chamber. The air then passes through one or more filters before leaving the vacuum cleaner, the filters being arranged to trap the dirt and debris within the dirt-collection chamber for subsequent disposal.
The dirt-collection chamber can contain or comprise a disposable bag, the wall of the bag also acting as a filter. Alternatively, the dirt-collection chamber is a receptacle which can be removed from the vacuum cleaner, emptied, and re-installed into the vacuum cleaner for re-use.
Many vacuum cleaners have a rotatable brush located adjacent to the opening of the suction head. The brush is rotated and engages the surface which is being cleaned. The brush helps to dislodge dirt and debris from the surface which is then gathered into the air flow and transported to the dirt-collection chamber.
Many vacuum cleaners are mains powered, and the manufacturers of mains powered vacuum cleaners will often seek to maximise the electrical and suction power of their vacuum cleaners in an attempt to increase their marketability. Typically, the opening of the suction head is surrounded by a wall which permits a relatively small air flow into the travelling head. The air is forced to pass underneath the wall, through the underlying carpet or other floor covering, whereby to dislodge dirt and debris from between the fibres of the carpet. As impellers are typically 10 to 40% efficient in use and air is not particularly good at dislodging dust, dirt and debris, this is a relatively inefficient method of cleaning. In order to achieve higher impeller efficiencies, manufacturers have tended to develop faster spinning impellers creating higher suction. However, as it is air flow rather than suction which dislodges dirt and debris, such vacuum cleaners generally do not achieve improved dirt and debris collection efficiency. Manufacturers have therefore tended to quote electrical and suction power as an indicator of the effectiveness of their appliances rather than cleaning efficiency.
It is also known to provide battery-powered vacuum cleaners. Battery-powered vacuum cleaners employing this traditional approach cannot provide the suction power of a mains powered vacuum cleaner without prejudicing the operating cycle of the vacuum cleaner, i.e. without unacceptably shortening the period between battery recharging, and therefore do not provide comparable cleaning performance.
Most domestic vacuum cleaners fall into two broad classes. The first class is often referred to as cylinder vacuum cleaners. In cylinder vacuum cleaners the suction head is connected to an operating handle which in turn is connected to a flexible hose through which the dirt and debris pass on their way to the dirt-collection chamber. The dirt-collection chamber is located within a body which is separate from the suction head and which also contains the motor, the body having wheels or slides by which it may be pulled across the floor during the cleaning operation.
The second class is often referred to as upright vacuum cleaners. In upright vacuum cleaners the motor and dirt-collection chamber are carried by, or in some cases are integral with, the operating handle, so that the body containing the motor and the dirt-collection chamber typically lie above the suction head during the cleaning operation.
The suction head of both classes of vacuum cleaner can be fitted with a rotating brush. Also, both classes of vacuum cleaner can incorporate a steering joint between the suction head and the operating handle, allowing the suction head to be steered in a chosen direction.
Because the suction head of a cylinder vacuum cleaner is connected to the body by way of a flexible hose, the suction head can be manoeuvred for “above-floor cleaning”, i.e. the cleaning of walls, stairs and the like. Also, the suction head can typically be removed from the hose and replaced by a dust brush, crevice tool, or other cleaning tool whereby to undertake a particular cleaning operation.
It is not possible to manoeuvre the suction head of an upright vacuum cleaner in the same way as that of a cylinder vacuum cleaner, and in order to enable above-floor cleaning the manufacturers of upright vacuum cleaners often provide an alternative solution. Specifically, the upright vacuum cleaner is typically fitted with a length of extendable flexible hose between the suction head and the dirt-collection chamber, the end of the hose adjacent to the suction head being releasable whereby the end of the released hose can be fitted with a cleaning tool and manoeuvred to the desired location without the user having to move the suction head. The flexible hose is typically made extendable so that during normal use of the vacuum cleaner the contracted hose can fit easily and conveniently upon the body of the vacuum cleaner. When released the hose can be extended to reach the desired location.
Once again, however, the hose is difficult to manoeuvre to the location of use, and the resilience of the hose increases the force which must be provided in order to reach less accessible locations. The force required often exceeds that required to tip over the vacuum cleaner, and it is known for an upright vacuum cleaner to fall over during periods of use of the extended hose.
The vacuum cleaner described in our patent application WO2012/085567 avoids or reduces many of the problems associated with battery powered vacuum cleaners, and can achieve cleaning performance similar to that of a mains powered vacuum cleaner.